Viavi Apex Enterprise G3-APEX-ENT-32T, User Manual

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Searching for microbursts
Chapter 10: Microbursts 243
when a microburst occurs, packets may be dropped, which causes them to be
retransmitted and that takes several milliseconds—nearly doubling the time to
complete the transaction. A 1-millisecond advantage in trading applications can
be worth $100 million a year to a major brokerage firm.
1
To prevent data loss because of microbursts, design your network so that its
capacity can withstand the highest possible burst of activity in whatever a time
frame you deem important (perhaps millisecond). Adding additional switches or
load-balancers to your network are a couple of possible solutions. This way the
link will never be constantly busy for more than one millisecond at a time, and no
data will be delayed on the link for more than one millisecond.
Another option is to smooth out any traffic or applications not sensitive to
latency or jitter sharing the same link. Using these options, you can optimize
your network for bandwidth efficiency, performance, or a combination of both
depending on each application’s requirements.
Even after identifying and correcting for all issues in your network, you may
still have problems with your Internet Service Provider. A study performed by
Microsoft Research indicates that microbursts are more likely to occur at edge or
aggregation links.
2
Therefore, it may be necessary to also have your ISP optimize
their flows to you.
Practically speaking, the capacity necessary to keep latency below one
millisecond is normally much less than the peak one millisecond data rate. This
is because many links use buffers to hold the traffic exceeding the link capacity
until the buffer can be cleared. Assuming the system can clear the buffer queue
quickly when the burst ends, microbursts are avoided because buffer capacity
was created.
In the Observer GigaStor Control Panel, a
microburst occurs when 1) the
maximum bits per duration interval based on the capture card speed and
utilization threshold you define is reached, and 2) the interval contains at least
two packets (full or partial).
There are a few different ways to search for microbursts using Observer Analyzer.
♦
Using triggers and alarms to inform you when microbursts occur.
Customize your triggers and actions and choose Microbursts from the
Alarms list.
♦
Using the Microburst Analysis tab is the easiest way to analyze large
chunks of time for microbursts and view the decoded packets.
♦
Using Network Trending for microbursts. This option is different than
the packet capture and decode option available through the Microburst
Analysis tab. First, packet capture does not need to be running for
Microburst trending to see any microbursts. Second, Microburst trending
can also be pushed to Observer Reporting Server and aggregated with
Microburst trending information from other probes in your network
so that you have a fuller picture of where and when microbursts are
occurring.
♦
Using the Detail Chart. This method is limited to a 15 minute time frame
on the Detail Chart.
1.
Information Week, April 21, 2007.
2.
Microsoft Research, June 1, 2009.